The disclosure relates to a current resonant power supply device, and particularly relates to a current resonant power supply device, which can achieve reduced power consumption under light load.
Japanese Patent Application Publication No. 2014-60895 (Patent Literature 1) and Japanese Patent No. 5384973 (Patent Literature 2) disclose current resonant power supply devices that can achieve reduced power consumption under light load.
The current resonant power supply device of Patent Literature 1 judges whether the device is currently in a light load state by comparing a power value detected by the power detection circuit with threshold Vref, and performs a burst oscillation operation while controlling the cycle of the burst oscillation if judging that the device is currently in the light load state.
The current resonant power supply device of Patent literature 2 detects the phase of current flowing through the switching elements. If the phase of the current thus detected is smaller than a predefined value, the current resonant power supply device judges that the device is currently in a light load state, and thus operates in a burst oscillation mode while operating the high side switch and the low side switch at unequal duty ratios.
Meanwhile, when changed to a standby load state, an Inductor Inductor Capacitor (LLC) current resonant system receives a standby signal received from outside, and switches from a normal mode to a standby mode.
Specifically, the standby signal is outputted from a system microcomputer on the secondary side of a transformer and is inputted into a power control integrated circuit (IC) on the primary side of the transformer via a photocoupler. For example, an SB terminal of the power control IC on the primary side of the transformer receives the standby signal from the photocoupler on the secondary side of the transformer.
The current resonant power supply devices of Patent Literatures 1 and 2 are capable of transitioning to a burst mode upon detection of a light load state.